Method for recording of data stream on multiple recording media

ABSTRACT

The method for recording data comprised in a real time data stream sequentially on multiple recording media reduces the buffer required to temporarily store data from the data stream by starting the change of recording medium when an interruption in the program to be recorded is detected. At least part of the data during the change of recording medium is of less interest to the user and the loss of this data is thus preferred over the loss of data belonging to the program that is to be recorded. By allowing selective loss of data the buffer size is reduced.

The invention relates to a method for recording data comprised in a realtime data stream sequentially on multiple recording media comprising thesteps of:

recording a first segment of the data stream on a first recording medium

buffering the data stream in a buffer while replacing the firstrecording medium

by a second recording medium

recording a second segment of the data stream on the second medium.

The invention further relates to a recorder using such a method.

Presently recorders for recording real time data streams have limitedrecording capacity. Whenever the recording medium is full the recordingmedium needs to be changed. The change can be either effected manuallyby the user or can be effected automatically for instance by using achanger mechanism. This change will always require some time duringwhich recording on the recording medium is not possible.

Consequently during this change the data in the data stream is lost.Losing the data presents a severe disadvantage for the user of therecorder intending to record for instance a long movie. A solution tothis problem is the use of a buffer to preserve the data until recordingis possible again. The size of the buffer must be large enough to storeall the data received by the recorder during the change of the recordingmedium. Such a buffer has the disadvantage that the price of therecorder is increased.

It is the objective of this invention to reduce the amount of bufferneeded and thus reduce the cost of the recorder.

This objective is achieved in that the invention is characterized inthat the first recording medium is being replaced by the secondrecording medium during a period between the first segment and thesecond segment when the data in the data stream is not intended to berecorded.

When changing the recording medium when the recorder receives data whichis not intended to be recorded the buffer can be reduced because thereis no need for the recorder to record this data and only a small bufferis needed to record the data during the short time period before a newrecording medium becomes available again for recording. This smallbuffer ensures that if data intended for recording arrives while thechange of recording medium is not yet completed, the data will not belost. Since not all data since the start of the change of recordingmedium needs to be buffered, the size of the buffer can be reduced.Smaller buffers require less memory and are thus less expensive.

An embodiment of the method is characterized in that that period iscomprised in an interruption of a program in the data stream where theprogram is intended to be recorded.

During an interruption of a program the data in the data stream is notintended to be recorded and consequently it is of no importance tobuffer this data. The size of the buffer can therefore be reducedcompared to the situation where the data in the interruption of theprogram also needs to be buffered and recorded.

A further embodiment of the method is characterized in that the periodis comprised in an advertisement.

Advertisements are not part of the program intended to be recorded andwhen a change of recording medium is effected during an advertisementthe size of the buffer can be reduced compared to the situation wherethe data of the advertisement also needs to be buffered and recorded

A further embodiment of the method is characterized in that the periodis comprised in a scene change.

During programs there are often scene changes. Since there is norelevant data in the scene change the change of recording medium can beeffected during a scene change and the size of the buffer can be reducedcompared to the situation where the data of the scene change also needsto be buffered and recorded

A further embodiment of the method is characterized in that the programis a sports program.

Sports programs are often interrupted for several reasons. This allowsthe change of the recording medium during this interruption because theloss of data during an interruption is less annoying to the viewer thanloss of data during the sports game. Many sports programs compriseinterruptions to the actual game. These interruptions may be integralpart of the game such as the pause between two sessions or unscheduledbut in either case the actual game itself has stopped at such a moment.

A further embodiment of the method is characterized in that theinterruption is due to an injury.

An injury of a participant of the sparts game is an unscheduled pause ina sports game and can thus be used to change the recording medium.

A further embodiment of the method is characterized in that theinterruption is due to a time out. A time out is of less importance to asports game than the actual game itself. During the time-out a loss ofdata is less annoying compared to data loss during the sports game. Asmaller buffer can therefore be used.

A further embodiment of the method is characterized in that the periodis comprised in a list of credits. Often the list of credits is of lessimportance to the user and it is less annoying if a part of the creditsis missing, compared to when part of a movie is missing. It is therefore advantageous to change the recording medium during the creditsbecause a loss of data can be tolerated, resulting in a smaller buffercompared to the situation when no data loss is tolerated.

A further embodiment of the method is characterized in that the periodis comprised in a section of the data stream where the data in the datastream has a low bit rate.

When selecting a section of the data stream where the bit rate of thedata stream is low, the size of the buffer can be reduced while stillrecording the entire data stream without loss of data. At a lower bitrate less buffer is used for recording a section of a given durationcompared to a section of equal duration but with a higher bit rate.

A further embodiment of the method is characterized in that the programis a music program and that the period is a period between a first songand a second song.

Music programs are particularly suited for applying the method accordingto the invention since music often comprises pauses. A pause can almostalways be found just before the start of a song as well as immediatelyafter a song. Using a smaller buffer the method can still start therecording while the change of recording medium has not yet beencompleted

A further embodiment of the method is characterized in that theinterruption is determined from an electronic program guide.

Electronic program guides indicate when a program starts, when it endsand when interruptions are scheduled. An example is a long movie whichis divided in two sections by a news cast. Changing the recording mediumduring the news cast is of no consequence since the news cast was notintended to be recorded anyway.

Most interruptions listed in an electronic program guide will be longerthan the time needed to replace the recording medium, in which case abuffer is not needed.

A further embodiment of the method is characterized in that a start ofthe interruption is determined from an information block transmittedtogether with the program.

The content provider can include an indication in the data stream thatan interruption is starting. This can be implemented in the same way ascurrently the German VPS system indicates the start and end of a programto start and stop the recording by a VCR. Alternatively this informationthat an interruption is starting can be transmitted to the recorder viateletext. Both systems allow the quasi real time transfer of thisinformation, allowing sufficiently exact control of the start of thechange of the recording medium.

In this way the recorder does not need to determine the content of thepicture or audio of the data stream but can use existing hardware in therecorder to determine the opportune moment for effecting the change ofrecording medium.

A further embodiment relates to a recorder for recording a program in adata stream using more than one recording medium using one of themethods as claimed in claims 1 to 10.

The invention will now be described based on figures.

FIG. 1 shows a data stream comprising a program that is intended to berecorded and the instances of change of recording medium and therequired buffering.

FIG. 2 shows a data stream comprising a program that is intended to berecorded when the instances of changing the recording medium coincidewith an interruption of the program and the effect on the requiredbuffering.

FIG. 3 shows a flow chart implementing the method according to theinvention

FIG. 4 shows a recorder for implementing the method according to theinvention.

FIG. 1 shows a data stream comprising a program that is intended to berecorded and the instances of change of recording medium and therequired buffering.

FIG. 1 shows a situation where the change of recording medium 9 is notaligned with an interruption 10 of the program but is in the middle ofthe third program section 7. In this situation there is no relationshipbetween the program content and the change of the recording medium 9because the change of recording medium 9 is based purely on therecording medium being full and a new recording medium being needed. Inorder not to lose data of the third program section 7 buffering 8 isneeded.

In contrast to this the method of the present invention does not changethe recording medium when the recording medium is full, but depending onthe content of the program intended to be recorded. This can result in achange of recording medium when the recording medium is not completelyfull.

This is also illustrated in FIG. 1.

The data stream 1 comprises a program intended to be recorded whichcomprises of three program sections 2, 3, 7 separated by two periods 4,10 which form interruptions to the program and effectively divide theprogram into the three program sections 2, 3, 7. When the program is toolarge too fit on a single recording medium and is to be recorded withoutlosing data of the program sections 2, 3, 7, the recording medium mustbe changed somewhere between the start of the first program section 2and the last program section 7. The first change 6 starts coincidingwith the start of the interruption and, in this example, takes less timethan the duration of the interruption 4, thus ending before the start ofthe second program section 3. Even if no buffering would be used thefirst program section 2 and the second program section 3 would still berecorded without loss of data. Thus if the change of recording medium isproperly aligned with a program interruption the objective of theinvention is achieved.

When some of the data in the first interruption 4 is to be recorded,buffering 5 is needed that buffers the data until the new recordingmedium is available for recording.

It is to be noted that the size of the buffer must in that case besufficient to not only buffer some of the data of the interruption 4,but must also be large enough to buffer the first part of the secondsection because when the new recording medium is available for recordingit will take some time to transfer the data in the buffer to therecording medium before the data of the first part of the second programsection 3 can be recorded.

FIG. 2 shows a data stream 1 comprising a program that is intended to berecorded when the instances 20, 21 of changing the recording mediumcoincide with an interruption 4, 10 of the program and the effect on therequired buffering.

In FIG. 2 the data stream 1, like in FIG. 1, comprises a programintended to be recorded which comprises three program sections 2, 3, 7seperated by two periods 4, 10 which form interruptions to the programand effectively divide the program into the three program sections 2, 3,7.

A reduction in buffer size can be achieved in the following manner.

When the change of recording medium 21 is aligned with the end of theprogram section 2, i.e. the start of an interruption 4, and the durationof the change of recording medium 20 is less than the duration of theinterruption 4 no buffer is needed at all because the recording startsagain on the new recording medium before the start of the next programsection 3, thus achieving the objective of the invention.

When the change of recording medium 21 is aligned with the start of theinterruption 10 but is of a longer duration than the interruption 10 abuffer is needed to buffer the data of the program section 7 followingthe interruption 10 until the recording medium is ready to accept thedata of the program section 7. Since the buffer doesn't need to be largeenough to buffer the entire interruption 10 it's size can be reduced,thus achieving the objective of the invention.

It should be noted that the detection of the interruption of the programcan be implemented in many different ways. Processing the data of theprogram, i.e. audio or video, to find scene changes, titles at thebeginning or the end of a program, advertisements, silence betweenpieces of music, i.e. between songs, absence of movement and many otherindications for the detection of interruption 4, 10 or sections whichare of less interest to the user have been contemplated in the prior artfor instance for removing advertisements from a recording and can beequally successfully employed for determining the optimum time accordingto this invention to change the recording medium. Further possibilitiesinclude the transmission of a signal by the content provider of theprogram intended for recording that an interruption starts, in a similarfashion as in the VPS system where the start of a program is indicatedand used by the recorder to start the recording of the program exactlyon time even if the start of the program is delayed.

A further option is to use information obtained from an electronicprogram guide to determine interruptions to the program and schedule thechange of recording medium accordingly.

The buffer can be a circulating buffer where only the most recentinformation is preserved i.e. where the older data is overwritten by thelatest data. That way the size of the buffer is used optimally since thefull buffer size is available at the start of the program sectionbecause the data already present in the buffer from before the start ofthe program section 3, 7 can be retrieved and recorded on the recordingmedium. The buffer area is after retrieval of the data available againfor buffering new data. This means that some data from the interruptioncan be recorded while the full buffer can still be used for storing thedata in the first part of the program section.

FIG. 3 shows a flow chart implementing the method according to theinvention

To detect an interruption the first step 30 of the method comprises themonitoring of the data in the data stream for particular types ofinterruptions. In the second step 31 a decision is taken whether asuitable interruption is found. If a suitable interruption is not foundthe method returns to the first step 30 to continue monitoring the datain the data stream. If a suitable interruption is found the methodproceeds to the third step 32 where the change of the recording mediumis started. After this the method proceeds to the fourth step 33 wherethe buffering is started. Depending on the size of the buffer and theobjective of buffering i.e. preventing any loss of data or toleratingloss of data of the interruption, the comprises the third step 32 andthe fourth step 33 can be interchanged. After the fourth step 33 themethod proceeds to the fifth step 34 where the completion of the changeof recording medium is determined. If the change of recording medium isnot yet completed the method will return to the fifth step 34 until thecompletion is detected. When the completion of the change of recordingmedium is detected the method proceeds to the sixth step 35 where thecontent of the buffer is being transferred to the new recording mediumnow available after the recording medium change. While the buffer isbeing transferred to the new recording medium the current data from thedata stream must still be stored in the buffer since the recordingmedium is not yet available for recording the current data.

Once the buffered data is stored on the recording medium the methodproceeds to the seventh step where the current data stream can berecorded on the recording medium directly without needing to use thebuffer in order to prevent data loss.

A buffer is often already present in a recorder for other purposes thanbuffering during a change of the recording medium but such a buffer canbe substantially smaller since the amounts of data that need to bebuffered in regular operation are substantially smaller than the amountof data arriving during the change of a recording medium which lastsseveral seconds.

FIG. 4 shows a recorder for implementing the method according to theinvention.

The recorder 40 comprises a data processing unit 41, a memory 42 and abasic engine 43. The recorder further comprises a recorder input 45where the data stream is received from an external source. The recorderinput is connected to the input 46 of the data processing unit 41. Thedata processing unit 41 performs multiple functions such as formattingthe data stream for recording and determining the recording strategy,and also performs the method as outlined in the description of FIG. 3.To be able to perform the method the data processing unit 41 performsthe detection of an interruption, issues the command to the basic engine43 to start a change of recording medium 44, directs data to the buffer42 over the bidirectional bus 47, retrieves the buffered data from thebuffer 42 or passes on the data directly to the basic engine when nobuffering is needed. To communicate with the basic engine abidirectional data bus is provided between the basic engine 43 and thedata processing unit 41. Both data and commands can be sent over such abus.

The replacement of the recording medium can be effected in differentways.

A disc changer, integrated into the recorder 40 can be used, for examplea so called carousel loader which is well known from CD players wheremultiple CDs can be inserted in a carousel and the carousel is rotatedto bring the correct CD to the reading position. In a recorder therecording medium can be brought to the recording position by the samecarousel mechanism.

Alternatively the recorder can be equiped with a single loading tray andthe loading tray can be automatically opened when it is decidedaccording to the method of the invention to change the recording medium.The user is alerted by opening the loading, possibly supported byaudio/visual alarms, and invited to insert a new recording medium byhand. The alert and invitation can be generated by means included in therecorder such as a buzzer or a light, but can also be generated by therecorder such that the alarm is produced through a television setconnected to the recorder 40.

The alarm sound is played through the speakers of a television set andthe invitation is displayed by the television set.

The data processing unit can determine the opportune moment to changethe recording medium from the video or audio content of the data streamor can simply extract control signals sent by the content provider alongwith the program in the data stream, for instance in the form of controlsignals comparable to the VPS system, or by teletext.

1. Method for recording data comprised in a real time data streamsequentially on multiple recording media comprising the steps of:recording a first segment of the data stream on a first recording mediumbuffering the data stream in a buffer while replacing the firstrecording medium by a second recording medium recording a second segmentof the data stream on the second medium characterized in that the firstrecording medium is being replaced by the second recording medium duringa period between the first segment and the second segment when the datain the data stream is not intended to be recorded.
 2. Method forrecording data comprised in a real time data stream as claimed in claim1, characterized in that the period is comprised in an interruption of aprogram in the data stream where the program is intended to be recorded.3. Method for recording data comprised in a real time data stream asclaimed in claim 1, characterized in that the period is comprised in anadvertisement.
 4. Method for recording data comprised in a real timedata stream as claimed in claim 1, characterized in that the period iscomprised in a scene change.
 5. Method for recording data comprised in areal time data stream as claimed in claim 2, characterized in that theprogram is a sports program.
 6. Method for recording data comprised in areal time data stream as claimed in claim 5, characterized theinterruption is due to an injury
 7. Method for recording data comprisedin a real time data stream as claimed in claim 5, characterized in thatthe interruption is due to a time out.
 8. Method for recording datacomprised in a real time data stream as claimed in claim 1,characterized in that the period is comprised in a list of credits. 9.Method for recording data comprised in a real time data stream asclaimed in claim 1, characterized in that the period is comprised in asection of the data stream where the data in the data stream has a lowbit rate.
 10. Method for recording data comprised in a real time datastream as claimed in claim 2, characterized in that the program is amusic program and that the period is a period between a first song and asecond song.
 11. Method for recording data comprised in a real time datastream as claimed in claim 2, characterized in that the interruption isdetermined from an electronic program guide.
 12. Method for recordingdata comprised in a real time data stream as claimed in claim 2,characterized in that the start of the interruption is determined froman information block transmitted together with the program.
 13. Recorderfor recording a program in a data stream using more than one recordingmedium using one of the method as claimed in claim 1.